JPH0874651A - Detecting device for inner state of cylinder of internal combustion engine - Google Patents

Abstract

PURPOSE: To enable the states of the inside of a combustion chamber (whether or not ignition has occurred, ignition timing, air-fuel ratio, etc.) to be detected with high precision. CONSTITUTION: A laser beam source 12 is made to emit a laser beam the wavelengths of which are selectively absorbed by gasoline. After the laser beam is made to pass through a space within a combustion chamber 5 by a pair of opposite optical elements 10, 11 arranged to face the inside of the combustion chamber 5, it is introduced into a photoelectric conversion element 14. Since the laser beam is absorbed depending on the concentration of gasoline present in the space between the pair of optical element 10, 11 and thus the intensity of the transmitted beam impinging on the photoelectric conversion element 14 varies, the concentration of gasoline in the mixture, i.e., the air-fuel ratio within the combustion chamber 5 can be detected through the detection of this variation. Also, since the air-fuel ratio is suddenly leaned by ignition, the observation of variations in the air-fuel ratio allows determining whether or not ignition has occurred. Also, ignition timing and ignition delay can be detected through the detection of a crank angle position at the time of ignition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the presence or absence of ignition in the combustion chamber of an internal combustion engine (hereinafter, also referred to as "in cylinder" or "in cylinder").
The present invention relates to an in-cylinder state detection device that detects an ignition timing or an air-fuel ratio of an air-fuel mixture.

[0002]

2. Description of the Related Art For example, engine combustion control (air-fuel ratio control,
In order to optimize ignition timing control, fuel supply timing control, etc.), it is important to know the in-cylinder state of the internal combustion engine (whether ignition is present, ignition timing, air-fuel ratio, etc.). A device for detecting the in-cylinder state of an internal combustion engine has been proposed.

For example, Japanese Patent Application Laid-Open No. 57-73647 discloses a device for detecting the presence or absence (specifically, preignition) of ignition of an air-fuel mixture introduced into a cylinder of an internal combustion engine. In this device, light in the combustion chamber is guided to a sensor by an optical fiber made of quartz glass or the like, and ignition is detected from the rise of the detected light.

Further, for example, the air-fuel ratio (A / A) of the air-fuel mixture in the combustion chamber is detected by detecting combustion light in the combustion chamber.
A device for measuring F) is known, and is disclosed in JP-A-1-247.
In the air-fuel ratio detection device disclosed in Japanese Patent No. 740, combustion light is taken out by an optical fiber embedded in a spark plug,
The extracted combustion light is photoelectrically converted, and the air-fuel ratio is detected based on the flame emission spectrum.

[0005]

However, the one disclosed in the above-mentioned Japanese Patent Laid-Open No. 57-73647 has a structure in which an extremely slight rise of the light amount caused by ignition is detected through an optical fiber. Therefore, it is easily affected by noise and the like. Further, it is not easy to distinguish between the ignition light and the spark discharge light from the spark plug, and it is difficult to detect ignition with high accuracy. It should be noted that the one disclosed in JP-A-1-247740 has a configuration capable of detecting the light in the combustion chamber through an optical fiber, so that it can be considered to function as an ignition detection device. -7364
There is a problem similar to that disclosed in Japanese Patent Publication No.

Further, since the air-fuel ratio detecting device disclosed in the above-mentioned Japanese Patent Laid-Open No. 1-247740 detects the air-fuel ratio by utilizing "combustion light that has grown relatively after ignition" detected by an optical fiber. , There are the following problems.
That is, as shown in FIG. 20, within the region (hollow cone region) where the combustion light is extracted by the optical fiber, not only the emission in the region A close to the end face of the optical fiber but also the emission in the region B relatively far from the end face is also extracted. Will be done.

Here, the air-fuel ratio may be different between the A region and the B region depending on the gas flow in the combustion chamber, and the flame emission spectrum is different when the air-fuel ratio is different. Further, if the distance from the end face of the optical fiber is different, the intensity thereof changes in inverse proportion to the square of the distance. Therefore, in the configuration in which the combustion light is taken out by the optical fiber, the light emission in the region where the air-fuel ratio is different and the distance is different is mixed and taken out. For example, in the vicinity of the spark plug which is the determinant of the ignition limit in the spark ignition type engine. Even if it is desired to accurately obtain the air-fuel ratio in the area A, there is a theoretical problem that the light emission in the area B affects the detection of the air-fuel ratio with high accuracy.

For this reason, conventionally, it is considered that the air-fuel ratio is constant in the hollow cone area, and the measurement hollow cone area is narrowed in the distance direction by shortening the time for capturing the flame emission to take out the combustion light. To realize air-fuel ratio detection. However, as described above, the air-fuel ratio in the hollow cone region is not always constant, and if the intake time is shortened, the intensity of the light extracted decreases, resulting in a decrease in measurement accuracy. .

Further, the air-fuel ratio in the vicinity of the spark plug, which is a factor that determines the ignition limit, shows a time-series variation that strongly depends on the injection timing in addition to the particle size of the fuel spray. Therefore, in order to control the air-fuel ratio near the spark plug at the ignition timing in order to improve the ignitability, it is desirable to detect the air-fuel ratio near the spark plug before ignition. Then, it is not possible to detect the air-fuel ratio before ignition,
There is a problem that the air-fuel ratio in the vicinity of the spark plug at the ignition timing cannot be accurately controlled.

Therefore, conventionally, there is no device capable of detecting ignition in the cylinder with high precision, and no device capable of simultaneously performing ignition detection and air-fuel ratio detection with high precision. Therefore, highly accurate combustion control of the engine cannot be performed based on the in-cylinder state of these engines. The present invention
It is made in view of such a conventional situation, ignition detection with high accuracy, a cylinder state detection device of an internal combustion engine capable of ignition timing detection, and at the same time highly accurately detect the air-fuel ratio in the combustion chamber even before ignition. It is an object of the present invention to provide an in-cylinder state detection device for an internal combustion engine, which in turn can optimize combustion control of the engine based on the detection results of these devices. Another object is to improve the accuracy of the in-cylinder state detection device.

[0011]

Therefore, an in-cylinder state detecting device for an internal combustion engine according to a first aspect of the invention faces a combustion chamber of the internal combustion engine as shown in FIG. 1 in order to detect ignition. A pair of optical elements consisting of a light-emitting side and a light-receiving side are arranged to face each other with a predetermined gap, and transmitted light intensity detecting means for guiding the light emitted from the light source to the photoelectric conversion element via the pair of optical elements; Ignition detecting means for detecting ignition in the combustion chamber based on fluctuations in the output of the photoelectric conversion element in the intensity detecting means.

According to the second aspect of the invention, the crank angle detecting means for detecting the crank angle of the engine, the output of the ignition detecting means, and the output of the crank angle detecting means for detecting the ignition timing are provided. Ignition timing detection means for detecting the ignition timing based on the. In the invention of claim 3, in addition to the configuration of the invention of claim 1 or the configuration of the invention of claim 2, in order to detect ignition (or ignition timing) and detect the air-fuel ratio in the cylinder. A cylinder pressure detecting means for detecting the cylinder pressure of the engine;
And an air-fuel ratio detecting means for detecting an in-cylinder air-fuel ratio based on the output of the photoelectric conversion element in the transmitted light intensity detecting means and the in-cylinder pressure detected by the in-cylinder pressure detecting means.

According to a fourth aspect of the present invention, the pair of optical elements in the transmitted light intensity detecting means are provided integrally with the ignition plug of the engine. In the invention according to claim 5, heating means for heating the pair of optical elements in the transmitted light intensity detection means, and heating control means under operating conditions for selectively operating the heating means according to engine operating conditions. , Are provided.

According to a sixth aspect of the present invention, heating means for heating the pair of optical elements in the transmitted light intensity detecting means, and a state of attachment of fuel to the pair of optical elements in the transmitted light intensity detecting means are detected. And a heating control means by adhesion detection for operating the heating means when a fuel adhesion state is detected by the fuel adhesion detection means.

[0015]

According to the in-cylinder state detecting device for an internal combustion engine according to the present invention having the above structure, in the transmitted light intensity detecting means, the light emitted from the light source is a pair of optical elements facing the combustion chamber. The photoelectric conversion element is guided through the gap between the elements, and when passing through the gap, the fuel existing in the space is attenuated. And
While the attenuation changes depending on the fuel concentration, the fuel concentration is rapidly diluted by ignition, so that ignition can be detected by observing the manner of this attenuation (that is, fluctuation in the detected value of the fuel concentration). Moreover, the light source is forcibly used to emit light of a wavelength that is easily absorbed by the fuel, so that it is possible to make it less susceptible to noise and the like as compared with the conventional one that detects an extremely slight rise of the light amount. . Furthermore, since the wavelength of the transmitted light that is easily absorbed by the fuel is different from the wavelength of the spark discharge light, it is not necessary to be affected by the spark discharge.

Therefore, since ignition can be detected with high accuracy, for example, preignition in a spark ignition type engine can be detected with high accuracy, and control for preventing the occurrence of preignition (ignition timing control or air-fuel ratio control) can be performed. ) Etc. can be performed with high accuracy. According to a second aspect of the invention, in addition to the configuration of the first aspect of the invention, a crank angle detecting means is provided so that the ignition timing can be detected. For example, an ignition delay period (=) in a spark ignition type engine (= Ignition timing-ignition timing, see Fig. 18).
Thereby, for example, the accuracy of air-fuel ratio control and ignition timing control for improving the ignitability and improving the engine operability by reducing the ignition delay period in a practical engine and the discharge energy of the spark plug are optimized. Thus, the air-fuel ratio control and the ignition timing control can be performed so that the ignition delay period can be obtained. Furthermore, it is also possible to measure the ignition delay in the compression ignition type engine (the period from the start of fuel injection to the ignition, which determines the premixed combustion ratio, which greatly affects the NOx production amount and noise). Yes, control of the injection rate of the fuel injection pump to reduce the ignition delay period (i.e., fuel injection start in order to form an air-fuel mixture that is easy to ignite and shorten the ignition delay to reduce the premixed combustion ratio) Acceleration of atomization of the initial spray, that is, change control of the injection rate pattern for increasing the initial injection pressure, etc.) can be performed effectively and highly accurately.

According to the third aspect of the invention, since the in-cylinder pressure detecting means is provided, the following operation can be achieved. That is, the attenuation of the transmitted light detected by the transmitted light intensity detecting means changes depending on the fuel concentration, but this also changes depending on the pressure change in the combustion chamber (in other words, the combustion chamber volume change). . Therefore, the fuel concentration (air-fuel ratio) can be detected by excluding the factor of the in-cylinder pressure based on the output of the photoelectric conversion element on which the transmitted light passing through the gap is incident and the in-cylinder pressure detected by the in-cylinder pressure detecting means. I did it. Therefore, by combining the highly accurate ignition detection and ignition timing detection with the highly accurate air-fuel ratio detection, the above-mentioned air-fuel ratio control and ignition timing control, or the optimization control of the discharge energy of the spark plug, can be performed with higher accuracy. Will be able to do.

In the fourth aspect of the present invention, when detecting the air-fuel ratio in the combustion chamber, the air-fuel ratio in the vicinity of the spark plug greatly affects the ignition limit, so that the pair of optical elements are integrated with the spark plug. By providing the ignition device, it is possible to accurately detect the ignition, ignition timing, or the air-fuel ratio in the vicinity of the spark plug, and to simplify the parts configuration, assembly and the like. Especially, if the optical path is arranged so as to cross the spark plug gap,
Ignition, ignition timing, air-fuel ratio, etc. can be detected with the highest accuracy in places that greatly affect ignitability (without preignition, etc. Since it is started in the gap), the air-fuel ratio control, the ignition timing control, or the optimization control of the spark plug discharge energy can be performed with higher accuracy.

According to the fifth and sixth aspects of the invention, when the liquid fuel adheres to the pair of optical elements, the adsorbed fuel absorbs light, whereby the fuel concentration can be accurately detected. Disappear. Therefore, a heating means for heating the pair of optical elements is provided, and the engine is operated under the engine operating conditions where the fuel adhesion is predicted, or the fuel adhesion state is detected, and the heating means is operated to adhere to the optical element. It was made possible to vaporize the fuel that was made earlier.

[0020]

EXAMPLES Examples of the present invention will be described below. In FIG. 2 showing the system configuration of the present embodiment, a fuel injection valve 3 is provided in an intake port 2 of an internal combustion engine 1, and the fuel injection is performed with respect to air taken in through an air cleaner and a throttle valve (not shown). Fuel is intermittently injected and supplied from the valve 3 to form an air-fuel mixture.

The air-fuel mixture is sucked into the combustion chamber 5 through the intake valve 4 and is ignited and burned by spark ignition by the spark plug 6. Exhaust gas from the engine 1 is discharged into the atmosphere via an exhaust valve, a catalyst, and a muffler (not shown). Here, an in-cylinder pressure sensor (in-cylinder pressure detection means) 7 for detecting the pressure in the combustion chamber 5 (in-cylinder pressure) is provided, and the cylinder head 8 forming the combustion chamber 5 is integrated with the spark plug 6. In addition, a cylindrical optical element 9 constituting the transmitted light intensity detecting means is inserted and held so that the optical path crosses the spark plug gap. Although the optical element 9 is described as being integrated with the spark plug 6 here, the optical element 9 is not limited to this and may be provided separately facing the combustion chamber.

As shown in FIG. 3, a pair of optical elements (triangular prisms) 10 and 11 are integrally provided at the tip of the cylindrical optical element 9 facing the combustion chamber 5. The pair of optical elements 10 and 11 are formed at their tips with a light beam which is incident from the base end face side of the optical element 9 serving as a base body and advances toward the inside of the combustion chamber 5 along the axial direction of the optical element 9. The optical element 10 on the light emitting side which is reflected by the optical surface toward the other optical element 11, and the optical element 10 which is arranged to face the optical element 10 with a predetermined gap therebetween, and which reflects the light beam reflected by the optical element 10. The optical element 11 on the light receiving side reflects the light toward the optical element 9 by the optical surface formed at the tip.

That is, the light beam is configured to travel in a U-turn through the combustion chamber 5 by the pair of optical elements 10 and 11, and the light beam travels from the optical element 10 to the optical element 11. When going towards, the gap between the two,
The optical element is passed through a space in the combustion chamber (here, it is configured to pass through the spark plug gap), and when the mixture exists in the combustion chamber 5 from the intake stroke to the ignition. The light beam is transmitted through the mixture through 10 and 11.

Although quartz, sapphire or the like is used as the material for the optical elements 9, 10 and 11, sapphire is preferably used in consideration of heat resistance and pressure resistance. 4 and 5 show an example in which the optical elements 9, 10 and 11 are formed by sapphire rods 24 and 25.
The laser light reflected by the 45 ° optical surface on the tip side of the sapphire rod 24 is designed to be integrally provided so as to project to the tip of the spark plug with the center electrode 23c and the ground electrode 23d.
It is designed to be incident on the sapphire rod 25 side through the spark gap between and.

According to this structure, the air-fuel ratio that affects the ignitability by the spark plug can be detected more accurately, and highly accurate air-fuel ratio control is possible without being affected by the air-fuel ratio variation in the combustion chamber 5. Is. The configuration in which the optical elements 10 and 11 (sapphire rods 24 and 25) are integrally provided with the spark plug 6 is not limited to the above. However, in the case of detecting the local air-fuel ratio in the combustion chamber 5, the air-fuel ratio of the spark gap portion of the spark plug 6 is detected, and the fuel injection is controlled based on the detection result so as to obtain the desired air-fuel ratio. Therefore, as shown in FIGS. 4 and 5, the optical elements 10 and 11 are arranged on both sides of the spark gap of the spark plug 6 so that the optical path in the combustion chamber 5 crosses the spark gap. Is preferred.

As the light beam, light having a wavelength that is selectively absorbed by the gasoline fuel used is used. Specifically, it is infrared light, and in this embodiment, laser light having a wavelength of 3.39 μm included in the infrared light region is used. The laser beam emitted from the laser source (light source) 12 that emits the laser light is an optical element 13 including a mirror and a prism.
Is bent in a direction parallel to the axis of the optical element 9 by
The light enters at a right angle to the base end face of the optical element 9 and proceeds. Then, it makes a U-turn by the pair of optical elements 10 and 11, passes through the optical element 9 again, and exits at a right angle from the base end face. The laser beam emitted from the optical element 9 is bent toward the photoelectric conversion element 14 by the optical element 13 and enters the photoelectric conversion element 14.

The above laser source 12 and optical elements 9, 10, 11
The (24, 25), 13 and the photoelectric conversion element 14 constitute the transmitted light intensity detecting means of this embodiment. The output of the photoelectric conversion element 14 and the detection signal from the in-cylinder pressure sensor 7 are input to a control unit 15 containing a microcomputer for controlling fuel injection by the fuel injection valve 3. The control unit 15 functioning as an air-fuel ratio detecting means detects the air-fuel ratio of the engine intake air-fuel mixture based on these detection signals, and controls the fuel injection based on the detected air-fuel ratio. The control unit 15 also functions as the ignition detecting means and the ignition timing detecting means of the present invention.

Here, the principle of air-fuel ratio detection and ignition detection using the transmitted light intensity detection means in this embodiment will be briefly described. The gasoline fuel used for engine 1 is generally
It has a property of selectively absorbing infrared light, and in the air-fuel mixture, the amount of absorption increases substantially in proportion to the gasoline concentration in the air-fuel mixture. That is, when the incident light intensity is I _O , the gasoline concentration is C, and the absorption coefficient is K, the absorption amount I is I = I _O
It can be expressed as exp ^-KC .

Therefore, if it is possible to irradiate the air-fuel mixture with infrared light of a predetermined intensity and detect how much infrared light is absorbed by the gasoline, the concentration of gasoline in the air-fuel mixture, in other words, the air-fuel ratio of the air-fuel mixture, is detected. The fuel ratio can be detected. on the other hand,
Since the air-fuel ratio dilutes rapidly due to ignition, it is possible to detect the ignition timing by observing the change in the air-fuel ratio (details will be described later) and the combination of the presence or absence of ignition and the crank angle position detection result. become. It should be noted that the light source is forcibly used to emit light having a wavelength that is easily absorbed by the fuel, so that it is less susceptible to noise and the like as compared to the conventional one that detects an extremely slight rise of the light amount. If the wavelength of the transmitted light that is easily absorbed by the fuel and the wavelength of the spark discharge light are different,
It is not affected by the spark discharge.

Here, in the present embodiment, the pair of optical elements 10 and 11 constituting the transmitted light intensity detecting means are arranged so as to face each other with the space in the combustion chamber 5 as a gap, and the laser light passes through the gap. Since the laser light is finally incident on the photoelectric conversion element 14, the laser light is absorbed by an amount commensurate with the gasoline concentration in the air-fuel mixture existing in the gap, and the laser light attenuated by the absorption is converted into the photoelectric conversion element 14. It will be incident.

Further, the fact that the absorption amount of the laser light (infrared light) is proportional to the gasoline concentration means that the absorption amount also changes due to the change of the pressure (cylinder pressure) in the combustion chamber. Therefore, the calibration characteristic based on the in-cylinder pressure is measured in advance (see FIG. 6), and the calculation characteristic of the air-fuel ratio using the output of the photoelectric conversion element 14 and the in-cylinder pressure detected by the in-cylinder pressure sensor 7 as parameters ( By setting the conversion map) in the control unit 15 in advance, the combustion chamber 5 can be operated from the intake stroke when the mixture is sucked to the ignition timing.
It is possible to calculate the local air-fuel ratio in the inside (see FIG. 7).

When the transmitted light intensity detecting means is used as an ignition detecting device or an ignition timing detecting device,
Since accurate air-fuel ratio detection is not necessary, calibration with the in-cylinder pressure is not so necessary. That is, it is sufficient if even a rapid change in the air-fuel ratio can be detected. Of course, if it is desired to improve the accuracy of ignition detection, the air-fuel ratio may be accurately detected.

The air-fuel ratio (local air-fuel ratio in the vicinity of the spark plug 6) detected as described above is used as control information for injection control (injection amount control, injection timing control) by the control unit 15. The air-fuel ratio in the vicinity of the spark plug at the ignition timing will determine the ignition limit, and is an important factor especially in a lean-burn engine in which the ignitability deteriorates. If the air-fuel ratio can be detected, it becomes possible to control the air-fuel ratio in the vicinity of the spark plug with high accuracy and stably obtain good ignitability.

Further, since the transmitted light intensity detected by the photoelectric conversion element 14 is influenced only by the air-fuel ratio state in the gap between the pair of optical elements 10 and 11, the local air-fuel ratio is changed to another combustion chamber area. It can be detected with high accuracy without being affected by the air-fuel ratio. As the fuel injection control using the detection result of the air-fuel ratio, the injection amount is feedback-controlled to match the detected air-fuel ratio with the target air-fuel ratio, and the rich peak timing of air-fuel ratio fluctuation overlaps with the ignition timing. By controlling the injection timing by the injection valve as described above, the air-fuel ratio near the spark plug can be controlled to a desired state. The injection control will be described later in detail.

On the other hand, based on the ignition detection result obtained by using the transmitted light intensity detecting means, for example, preignition in a spark ignition type engine can be detected with high accuracy.
Preignition generation prevention control (ignition timing control and air-fuel ratio control) can be performed with high accuracy. Furthermore, if the ignition timing is detected, the ignition delay period (= ignition timing-ignition timing, see FIG. 18) in the spark ignition type engine can be detected with high accuracy. The air-fuel ratio control and ignition timing control that improve the ignitability by improving the ignitability by shortening the period, and the air-fuel ratio that provides the ignition delay period that optimizes the spark plug discharge energy It becomes possible to perform fuel ratio control and ignition timing control. The case where the ignition timing detection result and the air-fuel ratio detection result are used at the same time will be described later.

By the way, when the optical elements 10 and 11 for guiding the laser light are arranged so as to face the inside of the combustion chamber 5 as described above, stains due to combustion adhere to the optical elements 10 and 11, and the amount of the stains is increased. There is a possibility that the absorption of the laser light (infrared light) by the gasoline fuel cannot be accurately detected by attenuating the laser light. As a method of correcting the influence of such dirt, as shown in FIG. 8, when there is almost no fuel in the combustion chamber 5 immediately before the intake valve is opened during the exhaust stroke, that is, immediately before the mixture is sucked, The output A ₁ of the photoelectric conversion element 14 is taken in. Then, using this output A ₁ as the reference intensity for normalization, the output Bn of the photoelectric conversion element 14 in the subsequent air-fuel ratio calculation period in the intake stroke (for example, a predetermined section before the ignition timing) is divided by the reference intensity A ₁ . a value Bn / a ₁ was the final detection value.

According to the above method, the reference intensity A ₁ is
It is detected under the condition that almost no fuel is present in the gap between the pair of optical elements 10 and 11, so it changes mainly due to the contamination of the optical elements 10 and 11 (including the decrease of output intensity due to deterioration of the laser source). It is estimated to be. If the reference intensity A ₁ decreases due to the progress of dirt, the output Bn of the photoelectric conversion element 14 is corrected to be increased, and the attenuation of the laser light due to dirt can be compensated.

However, according to the correction method described above, although the correction calculation can be performed relatively easily, it is not possible to detect the dirt at the same time as the air-fuel ratio calculation. Since the transmitted light intensity for fuel ratio calculation is detected, there is a risk of deviation from the dirt state during air-fuel ratio calculation, and there is no fuel in the gap between the pair of optical elements 10 and 11. Since the dirt level is estimated by, high precision correction cannot be expected.

As another method for correcting the influence of the dirt, a light source which emits light having a wavelength which is not absorbed by gasoline but is absorbed only by the dirt and attenuated is provided, and the light beam emitted from the light source is Passing through the optical elements 10 and 11 coaxially with the light of the wavelength absorbed by gasoline used for air-fuel ratio detection, as shown in FIG. 9, at the same time as the transmitted light intensity Bn of the light absorbed by gasoline, it is absorbed only by dirt. The wavelength absorbed by gasoline is detected by detecting the transmitted light intensity An of the light having a wavelength that is absorbed, and correcting the transmitted light intensity Bn with the transmitted light intensity An of the light that is absorbed only by the dirt (Bn / An). There is a method of correcting the attenuation due to the dirt of the light in the area.

According to this correction method, it is possible to estimate the contamination state at that time in synchronization with the calculation of the air-fuel ratio, and the contamination can be detected without being affected by the fuel existing in the pair of optical elements 10 and 11. Since it can be performed, a high-precision stain correction can be performed although the calculation load increases. Here, the function of the control unit 15 for detecting the air-fuel ratio (gasoline concentration) while correcting the dirt as described above is shown in FIG.
It will be described according to the flowchart of The flowchart of FIG. 10 is simplified and shown as common to the above two correction methods.

In the flow chart of FIG. 10, first, in S1, the correction light intensity An indicating the attenuation level of the laser light due to dirt is detected. Specifically, the output of the photoelectric conversion element 14 is taken in at the timing immediately before the intake valve is opened, or the transmission intensity of light having a wavelength that is not absorbed by gasoline and is absorbed only by dirt within the calculation period of the air-fuel ratio. Sequentially take in.

In the next step S2, the transmitted light intensity Bn for air-fuel ratio calculation is detected. Then, in S3, the transmitted light intensity Bn for air-fuel ratio measurement is divided by the light intensity An for correcting the stain amount, and the calculation result is set to I as the light intensity with the stain amount corrected. In S4, the gasoline concentration C (air-fuel ratio) is calculated based on the light intensity I after the stain correction and the in-cylinder pressure detected by the in-cylinder pressure sensor 7.

At S5, n indicating the data number of the air-fuel ratio calculated within the air-fuel ratio calculation period is incremented by 1, and the next S
At 6, it is determined whether or not it is within the actual measurement period of the air-fuel ratio (for example, a predetermined section before the ignition timing). Then, if it is not in the actual measurement section, the data number is reset in S7. If it is in the actual measurement section, the flow returns to S1 without performing the reset, and the air-fuel ratio calculation is repeated while performing the dirt correction, and the calculation result is obtained. Store in time series.

It should be noted that the transmitted light intensity A influenced by the amount of dirt
If n is lower than a predetermined value, it is determined that the desired transmitted light intensity cannot be detected, and the predetermined fail-safe mode may be set. By the way, in the above embodiment, the optical element 9 (air-fuel ratio detecting body) including the pair of optical elements 10 and 11 is arranged near the spark plug 6, but this is the electrode of the spark plug 6. In order to control the air-fuel ratio of the atmosphere and raise the ignition limit, it is desired to detect the air-fuel ratio at a position as close as possible to the spark plug 6 (electrode portion).
This is because it is preferable to integrally provide the spark plug 6 and the pair of optical elements 10 and 11 in consideration of the reduction of the number of parts, the assemblability, and the space efficiency in the cylinder head forming the combustion chamber. When it is not necessary to take this into consideration (for example, when conducting an experiment in a test room), the spark plug 6 and the pair of optical elements 10 and 11 need not be integrally provided.

Next, the state of the air-fuel ratio feedback control and injection timing control by the control unit 15 using the air-fuel ratio detected by the configuration shown in the above embodiment will be concretely described with reference to the flowchart of FIG. In the flowchart of FIG. 11, first, in S11,
The engine speed Ne is calculated based on the detection signal from the crank angle sensor 60. Further, in S12, the throttle valve opening detected by the throttle sensor (not shown) is read as a representative value of the engine load. The crank angle sensor 60
Is, for example, a built-in distributor (not shown) that can detect a crank unit angle signal output in synchronization with engine rotation, and the control unit 15 counts this signal for a certain period of time or a crank reference angle signal. The engine rotation speed Ne is detected by measuring the cycle of.

Then, in S13, as shown in FIG. 12, the target air-fuel ratio AFR is set by referring to the map in which the target air-fuel ratio is set in advance for each operating region corresponding to the engine load and the engine speed. The map that stores the target air-fuel ratio AFR shown in FIG. 12 is a lean region that sets a target air-fuel ratio that is significantly leaner than the theoretical air-fuel ratio, a theoretical air-fuel ratio region that sets the theoretical air-fuel ratio as the target air-fuel ratio, and a theoretical It is roughly divided into a rich region in which a target air-fuel ratio that is slightly richer than the air-fuel ratio is set.

In the next step S14, it is determined whether or not the current operating condition is in the lean range where the target air-fuel ratio AFR is set to an air-fuel ratio which is significantly leaner than the theoretical air-fuel ratio. Here, when it is determined that the region is lean,
The process proceeds to S15, where the air-fuel ratio calculated based on the output of the photoelectric conversion element 14 and the output of the in-cylinder pressure sensor 7 is stored in a time series in a predetermined section before the ignition timing. The minimum air-fuel ratio PAFM (the richest air-fuel ratio in the air-fuel ratio calculation section) at the air-fuel ratio that varies within the predetermined section is obtained (see FIG. 13).

Then, in S16, the target lean air-fuel ratio AFR is compared with the minimum air-fuel ratio PAFM to determine the rich lean of the minimum air-fuel ratio PAFM with respect to the target air-fuel ratio. Here, the minimum air-fuel ratio PA rather than the target lean air-fuel ratio
When it is determined that the FM is small (rich),
Proceeding to S17, the crank angle position TPAFM at which the minimum air-fuel ratio PAFM is obtained within the predetermined section where the air-fuel ratio detection is performed.
Ask for.

Further, in S18, the current ignition timing TIG is obtained, and in the next S19, the deviation TD between the crank angle position TPAFM at which the air-fuel ratio becomes the minimum and the current ignition timing TIG.
Calculate IFF. Further, in S20, the reference timing TINJ (injection start timing or injection end timing) of the current injection control is obtained.

Then, in S21, the reference timing TINJ is corrected by the deviation TDIFF,
The injection timing is advanced / retarded so that the timing at which the minimum air-fuel ratio PAFM is obtained matches the ignition timing TIG. That is, when the combustion is performed at an air-fuel ratio that is significantly leaner than the stoichiometric air-fuel ratio, the ignitability deteriorates, so even if the average air-fuel ratio is lean, the air-fuel ratio near the spark plug is as rich as possible. Ignition in this state enhances ignitability. Therefore, the variation of the air-fuel ratio in the predetermined section before the ignition timing is obtained, and the injection timing is shifted so that the timing when the air-fuel ratio becomes the richest overlaps the ignition timing. Specifically, when the crank angle position TPAFM appears earlier than the ignition timing TIG, the injection timing is retarded by an amount corresponding to the deviation TDIFF.

In the correction control of the injection timing,
It is preferable to allow the change of the injection timing only within a predetermined range around the basic injection timing. When the operating state changes, the injection timing is once returned to the reference timing TINJ of the operating state, and the crank angle position TPA is again set.
It is advisable to make FM coincide with the ignition timing TIG. On the other hand, the injection amount correction for matching the spark plug vicinity air-fuel ratio with the target air-fuel ratio is performed outside the lean air-fuel ratio region, and the lean air-fuel ratio PAFM is determined to be leaner than the target air-fuel ratio in S16. This is performed in S22 to S25 in the air-fuel ratio range.

At S22, the average value MAFM of the air-fuel ratio successively calculated within the predetermined section before the ignition timing is calculated. Next, in S23, the target air-fuel ratio AFR and the average air-fuel ratio MAF
The deviation AFDIFF from M is calculated. In S24, the current injection amount QTp is set, and in the next S25, the deviation AF is set.
Corrected injection amount QAFDIF set corresponding to DIFF
F is added to the injection amount QTp for correction.

According to the correction control of the fuel injection amount, 1
It is possible to obtain the deviation of the actual air-fuel ratio from the target air-fuel ratio for each cycle, and to correct the deviation according to the deviation in the fuel injection amount in the next cycle. It can be controlled. In the control of the injection timing and the control of the injection amount as described above, it is desired to detect the air-fuel ratio of the ignition atmosphere of the spark plug 6 with high accuracy, so that the optical elements 10 and 11 are provided between the electrodes of the spark plug 6. It is desirable to detect the transmitted light intensity with the configuration of the embodiment shown in FIGS. 4 and 5 which is integrated with an ignition plug as a configuration for passing laser light.

In the above description, the deviation AFDIFF is converted into the injection amount data. However, the correction coefficient of the injection amount is set from the deviation AFDIFF, and the basic injection amount is multiplied by the correction coefficient to perform the correction. May be. Further, in the present embodiment, the air-fuel ratio of the air-fuel mixture actually sucked into the combustion chamber by the fuel injected from the fuel injection valve 3 can be detected,
For example, wall flow correction during transient operation or cold can be optimized based on the air-fuel ratio detection result. That is, the fuel injection valve 3
The fuel injected and supplied from the fuel tank has a transportation delay due to collisions and adherence to the wall surface, and during transient operation or during cold, it is necessary to correct the fuel consumption increase in consideration of such delay. For example, since the air-fuel ratio in the combustion chamber can be detected for each cycle, excess or deficiency of the increase correction can be quantitatively detected, and thereby the increase correction amount for transient operation or cold operation can be optimized.

In the control of the injection timing in the above embodiment, the state of the air-fuel ratio fluctuation before ignition is detected in time series,
The timing at which the air-fuel ratio peaks on the rich side is obtained based on the detection result, and the deviation amount between the rich peak timing and the ignition timing is used as the correction amount of the injection timing, but the injection timing is advanced / retarded, The injection timing at which the air-fuel ratio at the ignition timing becomes a rich peak may be found by detecting the changing direction of the air-fuel ratio at the ignition timing based on the correction result.

An example of such injection timing control is shown in FIG.
It is shown in the flowchart of 14. First, in S51, the basic injection timing (injection start crank angle or injection end crank angle) preset according to the operating conditions is read from the map. Then, in S52, fuel injection is performed in accordance with the basic injection timing, and in next S53, the air-fuel ratio of the air-fuel mixture formed by such fuel injection is detected by the photoelectric conversion element 14 as described above. The ignition timing is calculated based on the light intensity and the cylinder pressure.

At S54, the air-fuel ratio calculated at S53 is compared with the air-fuel ratio at the previous ignition timing to determine whether the air-fuel ratio at the ignition timing has changed in the rich direction as compared with the previous time. . When the air-fuel ratio at the ignition timing is changing in the rich direction, the routine proceeds to S55, where the air-fuel ratio calculated at this ignition timing is stored as the previous air-fuel ratio.

Next, in S56, it is determined whether or not the injection timing was advanced by the previous injection timing correction. Here, when it is determined that the air-fuel ratio of the ignition timing has changed in the rich direction as a result of advancing the injection timing, the air-fuel ratio of the ignition timing may change more richly by advancing the injection timing. Therefore, the process proceeds to S57, and the injection timing for advancing the injection timing by a predetermined minute angle is corrected. Then, in S58, the history of correction that further advances the injection timing is stored.

On the other hand, when it is determined in S54 that the air-fuel ratio at the ignition timing has not changed in the rich direction compared to the previous time, the routine proceeds to S59, where it is determined whether or not the previous correction of advancing the injection timing has been performed. As a result of advancing the injection timing, if the air-fuel ratio does not change in the rich direction,
Proceeding to S60, on the contrary, the injection timing is corrected by delaying it by a predetermined minute angle, and in S61, the history of the correction of delaying the injection timing is stored.

When it is determined in S59 that the air-fuel ratio does not change in the rich direction as a result of delaying the injection timing, conversely, in order to advance the injection timing, S
Continue to 57. That is, for example, when the air-fuel ratio at the ignition timing changes in the rich direction by advancing the injection timing, the injection timing is gradually advanced until the change in the rich direction stops and the change in the rich direction stops. This time, by conversely delaying, the injection timing is controlled so that the vicinity of the rich peak coincides with the ignition timing.

When the advance / retard correction of the injection timing converges as described above, the injection timing at that time may be learned and stored for each operating condition. In the above-mentioned embodiment, the embodiment is shown in which the injection timing or the injection amount is corrected based on the air-fuel ratio detected based on the transmitted light intensity of the laser light, but the injection hole of the fuel injection valve is made to face the combustion chamber. By using the air-fuel ratio detection result of the above configuration for injection pressure control in a direct injection spark ignition engine (see Japanese Patent Application No. 4-17738) configured to perform fuel injection during the compression stroke, the direct injection spark ignition engine The ignition performance can be improved.

That is, in the case of performing lean combustion in the direct injection spark ignition engine, it is desired to stratify the air-fuel ratio in the vicinity of the spark plug to make it richer than others, and for that purpose, atomization by the fuel injection valve is required. Should be directed near the spark plug. By the way, the pair of optical elements 10 and 11 (sapphire rod 2
The correction of the transmitted light intensity with respect to the dirt of (4, 25) has already been described, but since the vaporization property of the fuel deteriorates during cold start, the fuel becomes a wall flow and flows into the combustion chamber 5, There is a possibility that the liquid fuel adheres to the optical elements 10 and 11 projecting into the inside 5, and the liquid fuel adheres to cause attenuation of light intensity exceeding the limit of the correction control.

Therefore, for example, as shown in FIG. 15, with respect to the pair of optical elements 10 and 11 shown in FIGS. 3 to 5, the bottom surface of the gap between the optical elements 10 and 11 (the end surface of the optical element 9) is shown. A heater (ceramic heater) 31 as a heating means is attached to
The heater power supply line 32 is embedded in the optical element 9 and taken out to the outside. Then, when the liquid fuel adhesion is in an engine operating condition predicted, or when the adhesion state is detected from the change in the calculated air-fuel ratio, the control unit 15 controls the power supply to the heater 31. Heat is generated and the optical elements 10 and 11 are warmed by such heat generation so that the attached liquid fuel is vaporized early.

The optical elements 10 and 11 shown in FIG.
Although it is of a different type from the spark plug 6 shown in FIG. 5, the heater 31 can be attached in the same manner even in the case of being integrated with the spark plug 6 as shown in FIGS. The heater control, which will be described later, is performed according to the common specifications regardless of whether the spark plug 6 is an integral type or a separate type. According to the flowchart of FIG. 16, the state of concrete heater control
This will be described with reference to FIGS. 2 and 15.

The software function of the control unit 15 shown in the flow chart of FIG. 16 corresponds to the heating control means according to the operating conditions, the fuel adhesion detection means and the heating control means by the adhesion detection. In the present embodiment, such heating is performed. As will be described later, the signals from the water temperature sensor 61 and the start switch 62 (see FIG. 2) are used to determine the control condition.

In the flowchart of FIG. 16, first, S
At 31, the cooling water temperature Tw detected by the water temperature sensor 61 is compared with a predetermined temperature. Then, when it is determined that the cooling water temperature Tw representing the engine temperature is lower than the predetermined temperature, the process proceeds to S32, and the elapsed time Ta from the start measured based on the signal of the start switch 62 and the predetermined time To compare.

Here, if it is determined that the elapsed time Ta from the start has not reached the predetermined time, the process proceeds to S33, the power is supplied to the heater 31 and the heater 31 is heated to generate the optical element 10. , 11 is heated. That is, the heater 31 is caused to generate heat within a predetermined period immediately after the cold start, and the optical element
This is for heating the liquids 10, 11 and by this, even if liquid fuel flows into the combustion chamber 5 and adheres to the optical elements 10, 11, such liquid fuel can be vaporized at an early stage. The accuracy of the air-fuel ratio detection performed by passing the laser light through the air-fuel mixture via the elements 10 and 11 can be maintained even during cold starting.

On the other hand, in a lean burn engine or the like, fuel injection may be performed during the intake stroke. With such a configuration, even if it is not immediately after cold start as described above,
The injected fuel is directly sucked into the combustion chamber 5 so that the optical elements 10 and 11 (sapphire rods 24 and 25)
Liquid fuel may adhere to the. Here, when the liquid fuel adheres, the laser light is largely absorbed by the adhered fuel, so that the calculated air-fuel ratio rapidly changes in the rich direction.

Therefore, the calculated first-order differential value AFDIF of the air-fuel ratio is calculated within the air-fuel ratio calculation period (see FIG. 17), and the cooling water temperature Tw and the post-start time Ta are equal to those of the liquid fuel for the optical elements 10 and 11. Even if the adhesion condition is not satisfied, the primary differential value AFDIF is compared with a predetermined value in S34, and when a large change in the calculated air-fuel ratio value is detected, the liquid is fed to the optical elements 10 and 11. It is estimated that the static fuel is attached, and the process proceeds to S33, in which power is supplied to the heater 31.
The detection of the adhesion state based on such an air-fuel ratio differential value shows the function of the control unit 15 as the fuel adhesion detection means.

In the heater control based on the differential value AFDIF of the air-fuel ratio, in order to avoid frequent ON / OFF control due to the variation of the differential value, a hysteresis is provided in the determination level or the adhesion state is temporarily set. It is preferable that the ON-OFF control condition is such that the current is forcibly energized continuously for a predetermined time when detected, or that the differential value is stable below the judgment level for a predetermined time or more.

As described above, in the case where the liquid fuel adhesion to the optical elements 10 and 11 is detected from the fluctuation of the calculated air-fuel ratio, the fuel adhesion state that does not correlate with the engine operating conditions such as the cooling water temperature Tw is detected. Even in an engine that can detect and inject fuel during the intake stroke, the optical element 1
The state of liquid fuel adhesion to 0 and 11 can be eliminated early to maintain the air-fuel ratio detection accuracy.

On the other hand, immediately after the cold start and when the calculated air-fuel ratio is still stable, the routine proceeds to S35, where the heater 31
Stop the power supply to and avoid unnecessary power consumption.
It should be noted that the optical elements 10 and 11 (sapphire rods 24 and 25) are integrally formed with the spark plug by the structure shown in FIGS.
When the heating control is performed by the heater 31 in the above-described manner, the adhesion of the liquid fuel to the optical elements 10 and 11 also makes it possible to estimate the wetting of the electrode portion of the spark plug 6 with the fuel. By heating 10 and 11, the electrode part of the spark plug is also heated at the same time, and there is a secondary effect that deterioration of ignitability due to wetting of the spark plug can be avoided.

In the above heater control, the cooling water temperature Tw was used as a parameter representing the engine temperature, but it is obvious that the temperature of the lubricating oil, the temperature of the intake port, etc. may be used. . Next, the principle of ignition detection in the present embodiment will be described in detail based on FIG. 18, and an example of control that simultaneously uses the ignition timing detection result and the air-fuel ratio detection result will be described below.

As described above, the detection result of the air-fuel ratio suddenly becomes lean as the air-fuel mixture in the cylinder ignites and burns. Here, in FIG. 18, A / with respect to the crank angle (CA)
F, the differential value (A / F ') of A / F, and the in-cylinder pressure history are shown.
As shown in FIG. 18, when the air-fuel mixture is ignited and burned, the gasoline fuel contained in the air-fuel mixture is consumed, and as a result, the amount of gasoline that absorbs infrared rays decreases and the A / F rapidly becomes lean. Differentiating this history gives an extreme value. That is, this maximum value indicates ignition, and the crank angle (CA) at which this maximum value appears is the ignition timing.

By the way, the ignition timing is controlled by the control unit 15 under engine operating conditions (rotational speed, load, water temperature,
It is a value set based on the air-fuel ratio, etc.), but as shown in FIG. 18, it may take a predetermined time from ignition to ignition start, and this delay is the ignition delay period (or time).
(= Ignition timing-ignition timing). In this embodiment, the air-fuel ratio in the vicinity of the spark plug 6 in the cylinder and the ignition delay period can be detected at the same time, and therefore, as shown in FIG.
The ignition delay period with respect to the air-fuel ratio can be detected by a practical engine.

Since this ignition delay period also has a correlation with the discharge energy, the minimum required discharge energy can be obtained for the practical engine based on the detection result shown in FIG. Therefore, the durability of the spark plug 6 affected by the magnitude of the discharge energy, the battery life, etc. can be improved. Further, according to the present embodiment, the ignition delay in the compression ignition type engine (the period from the start of fuel injection to the ignition, the period determines the premixed combustion ratio, N
It is also possible to measure Ox production amount and noise, and to control the injection rate of the fuel injection pump so as to reduce the ignition delay period (that is, to form an air-fuel mixture that is easy to ignite and set the ignition delay. In order to reduce the premixed combustion ratio by shortening, it is possible to promote the atomization of the spray at the initial stage of fuel injection, that is, the change control of the injection rate pattern that increases the initial injection pressure, etc., effectively and with high accuracy. Therefore, it is possible to reduce exhaust emission and noise.

[0077]

As described above, according to the first aspect of the present invention, ignition detection can be performed with higher accuracy than in the prior art. For example, preignition detection in a spark ignition type engine can be performed with higher accuracy. Therefore, the preignition occurrence prevention control (ignition timing control and air-fuel ratio control) can be performed with high accuracy.

According to the second aspect of the present invention, the ignition timing can be detected with high accuracy, which is effective in, for example, engine operation experiments, and also reduces the ignition delay period in a practical engine, for example. The accuracy of the air-fuel ratio control and ignition timing control to improve the ignitability and engine operability, and the air-fuel ratio control and ignition to obtain the ignition delay period in which the discharge energy of the spark plug is optimized. The timing can be controlled. Also, it is possible to measure the ignition delay in the compression ignition type engine, and based on the detection result,
For example, it is possible to effectively and accurately control the injection rate of the fuel injection pump.

According to the third aspect of the present invention, the ignition detection or ignition timing detection and the local air-fuel ratio in the combustion chamber can be simultaneously detected with high accuracy. In particular, the air-fuel ratio in the vicinity of the spark plug can be detected. Can be detected before ignition, so that the air-fuel ratio in the vicinity of the spark plug at the ignition timing can be controlled with high accuracy, and the ignitability by the spark plug can be maintained at the optimum level. Further, the above-mentioned air-fuel ratio control, ignition timing control, or optimization control of the discharge energy of the spark plug can be performed with higher accuracy.

According to the fourth aspect of the present invention, when detecting the air-fuel ratio in the combustion chamber, the air-fuel ratio in the vicinity of the spark plug greatly affects the ignition limit, so that the pair of optical elements are integrated with the spark plug. By such provision, it is possible to accurately detect ignition, ignition timing, or air-fuel ratio in the vicinity of the spark plug, and to simplify parts configuration, assembly and the like. Especially, if the optical path is arranged so as to cross the spark plug gap,
Ignition, ignition timing, air-fuel ratio, etc. can be detected with the highest accuracy in a place that greatly affects ignitability, and as a result, the above-mentioned air-fuel ratio control, ignition timing control, or spark plug discharge energy Optimization control can be performed with higher accuracy.

According to the fifth and sixth aspects of the present invention, the optical element is heated when an operating condition or an attached state in which the liquid fuel is expected to be attached to the optical element is detected. Therefore, it is possible to avoid deterioration of the air-fuel ratio detection accuracy due to the adhesion of the liquid fuel.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a system schematic diagram showing one embodiment of the present invention.

FIG. 3 is a side view showing an ignition plug in which an optical element is integrated.

FIG. 4 is an enlarged view of the optical element section of FIG.

5 is a bottom view of FIG.

FIG. 6 is a diagram showing an air-fuel ratio corresponding to transmitted light intensity and in-cylinder pressure.

FIG. 7 is a diagram showing changes in transmitted light intensity and in-cylinder pressure according to a crank angle.

FIG. 8 is a diagram showing characteristics of stain correction based on light intensity immediately before the intake valve is opened.

FIG. 9 is a diagram showing characteristics of stain correction using lights of different wavelengths.

FIG. 10 is a flowchart showing a state of air-fuel ratio calculation accompanied by correction of dirt.

FIG. 11 is a flowchart showing fuel injection control using the air-fuel ratio detection result.

FIG. 12 is a diagram showing a map of a target air-fuel ratio.

FIG. 13 is a diagram showing characteristics of air-fuel ratio detection for fuel injection control.

FIG. 14 is a flowchart showing another embodiment of injection timing control.

FIG. 15 is a structural diagram showing an embodiment in which a heater is attached to an optical element.

FIG. 16 is a flowchart showing ON / OFF control of a heater.

FIG. 17 is a diagram showing a relationship between a differential value of air-fuel ratio detection data and heater control.

FIG. 18 is a diagram showing the relationship between the differential value of the air-fuel ratio detection data and the ignition delay.

FIG. 19 is a diagram showing optimum discharge energy.

FIG. 20 is a diagram for explaining a problem of conventional air-fuel ratio detection using combustion light.

[Explanation of symbols]

 1 Internal Combustion Engine 2 Intake Port 3 Fuel Injection Valve 4 Intake Valve 5 Combustion Chamber 6 Spark Plug 7 Cylinder Pressure Sensor 8 Cylinder Head 9, 10, 11, 13 Optical Element 12 Laser Source 14 Photoelectric Conversion Element 15 Control Unit 21 Holder 23 Spark Plug Main unit 23c Center electrode 23d Ground electrode 24, 25 Sapphire rod 31 Heater 60 Crank angle sensor 61 Water temperature sensor 62 Start switch

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location G01N 21/59 Z

Claims (6)

[Claims] 1. A pair of optical elements consisting of a light emitting side and a light receiving side facing each other in a combustion chamber of an internal combustion engine with a predetermined gap therebetween, and light emitted from a light source is photoelectrically converted through the pair of optical elements. A transmitted light intensity detection unit that guides the element, and an ignition detection unit that detects ignition in the combustion chamber based on a change in the output of the photoelectric conversion element in the transmitted light intensity detection unit. In-cylinder state detection device for internal combustion engine. 2. A crank angle detecting means for detecting a crank angle of an engine; an ignition timing detecting means for detecting an ignition timing based on an output of the ignition detecting means and an output of the crank angle detecting means. The in-cylinder state detection device for an internal combustion engine according to claim 1, wherein the in-cylinder state detection device is configured to include. 3. An in-cylinder pressure detecting means for detecting an in-cylinder pressure of an engine, and an in-cylinder pressure inside the cylinder based on an output of the photoelectric conversion element in the transmitted light intensity detecting means and an in-cylinder pressure detected by the in-cylinder pressure detecting means. An in-cylinder state detection device for an internal combustion engine according to claim 1 or 2, further comprising: an air-fuel ratio detecting means for detecting an air-fuel ratio. 4. The internal combustion engine according to claim 1, wherein the pair of optical elements in the transmitted light intensity detecting means are provided integrally with an ignition plug of an engine. In-cylinder condition detection device. 5. A heating means for heating the pair of optical elements in the transmitted light intensity detecting means, and a heating control means under operating conditions for selectively operating the heating means according to engine operating conditions are provided. The in-cylinder state detection device for an internal combustion engine according to any one of claims 1 to 4, characterized in that. 6. A heating means for heating the pair of optical elements in the transmitted light intensity detecting means, and a fuel adhesion detecting means for detecting an adhesion state of fuel to the pair of optical elements in the transmitted light intensity detecting means, 5. A heating control means by adhesion detection for operating the heating means when the adhesion state of fuel is detected by the fuel adhesion detection means, any one of claims 1 to 4 is provided. An in-cylinder state detection device for an internal combustion engine according to item 1.